Replacing images is done in the "Attachments" page. This is the easiest, safest and quickest method to replace images. If you use a sidebar and your site's width becomes too narrow, the images will overlap. To fix this, make them smaller.
- learn how the "Attachments" page works
- learn how to use the "replace" feature in the "Attachments" page
- if you use a sidebar and your site's width becomes too narrow, the images will overlap. To fix this, make them smaller. or do not use the sidebar.